Mycophenolate mofetil (RS 61433) is an immunosuppressant compound which has been approved in over 30 countries (including USA, European countries, Canada and Australia) for prophylaxis of acute renal transplant rejection. Mycophenolate mofetil (MMF) reversibly inhibits the proliferative response of human peripheral blood mononuclear cells (PBMCs) to T and B cell mitogens in vitro, as does its primary metabolite mycophenolic acid (MPA). It also inhibits immunoglobulin formation by human B cells in response to polyclonal stimulators.